Vízügyi Közlemények, 1982 (64. évfolyam)

2. füzet - Sziámik Lajos : AZ 1980-81. ÉVI KÖRÖS-VÖLGYI ÁRVIZEK HIDROLÓGIAI JELLEMZÉSE

\ Az 1980—81. évi Körös-völgyi árvizek 199 The flood in July —August, 1980 was due to high-intensity rainfalls (Mrs. Homoki, Mrs. Makai, Takács, 1981), whereas that in March, 1981, to combined rain- and snowmelt runoff ( Fig. 19). In quest of the causes controlling the flood characteristics in the Körös Basin the author has analysed in detail the extraordinary features of the meteorological situations and the hydrological conditions. During the past 15 years both the flood stages and the flood discharges can be observed to have increased rapidly in the Körös River Basin (Table III

). This increase is most spectacular on the Ant gage on the Fekete-Körös River (Fig. 1 ), where the stages were on five occasions between 1966 and 1980 higher than the highest on record previously and the total rise was 1.72 m (Fig. 24). Further investigations have revealed that between 1915 and 1981 flood peaks with stages exceeding the flood warning degree III occurred on 22 occasions on the Fekete-Körös and on 26 occasions on the Fehér-Körös rivers. The floods since 1966 are among the first five as regards the total runoff volume conveyed (Table V

). The summer flood of 1980 was the highest on record thus far in the Körös River Basin (Fig. 18). The rainfall pattern in 1980 differred from that accepted as normal during the last decades, since for eacli of the successive several rain storms highest intensities were recorded in the mountain catchments of the Fekete- and SebesKörös rivers, with unprecedented 24-hour rain depths in these areas. The earlier rain patterns were either uniformly distributed over the entire catchment, or extended over the sub-catchments of the two southern-, or the two northern tributaries only. The rate of rise was also unprecedented on the Fekete-Körös River (Fig. 14), where owing to the low water during the antecedent period, the flood wave ancroached upon a virtually empty bed and travelled down the river with a steepslope never observed before ( Fig. 2). The flood discharge surpassed more than 1.5 times the highest on record that far. The check on the runoff history in terms of the volumes conveyed (Fig. 16) yielded a detailed picture about the runoff events. The flood in March, 1981, on thé Fekete- and Fehér-Körös rivers was similar in type to that assumed in dimensioning the emergency flood reservoir at Mályvád (Szlávik 1978, 1980). The peak flood discharge on the Fekete-Körös River approached that in 1980, while on the Fehér-Körös River it was higher by 35 per cent than that in 1974, i.e., the highest recorded previously (Table IV). The stages observed after opening the Mályvád emergency reservoir are shown in Fig. 21. Without resort to the emergency reservoir the peak stages on the Fekete-, Fehér- and Kettős-Körös rivers would have surpassed substantially those on record so far (Fig. 22). * * * Caractérisation hydrologiquc des crues de vallée de Körös de 191>0—lOJtl SZLÁVIK L. Au cours des années de 1980 et 1981 deux crues exceptionnelles sont passées dans la vallée des Körös. Les conditions génératrices hydrométéorologiques de crue ont eu leur propres caractéristiques différentes, ainsi les évolutions des ondes de crues ont différé de l'une à l'autre. La crue de juillet et d'août en 1980 a été provoqué par des pluies à forte intensité (Mme Homoki —Mme Makai — M. Takács 1981), cependant celle de mars a été généré par la coincidence des pluies et de la fonte de neige (Fig. 19). Recherchant les causes des caractéristiques de crue des Körös, l'Auteur a analysé en détaille l'exceptionnalité des facteurs des conditonnes météorologiques et des circonstances hydrologiques. Durant des 15 années écoulées on peut constater une augmentation rapide du niveau et du débit de crue dans la vallée des Körös (Tableau III.). Cette augmentation est spectaculaire surtout à la section de Ant de la rivière de Fekete-Körös (Fig. 1.), où on a enregistré cinq records des niveaux de crue, et l'accroissement est de 1,72 m (Fig. 24) au cours de la période de 1966 à 1980.